This invention relates to a picture output apparatus for allowing picture data including character code, graphic command and/or image data to undergo picture output in the state developed into bitmap data.
Picture data prepared by using picture preparation application software, or any other technique on the host computer are adapted so that when user inputs picture output instruction through input device such as keyboard or mouse, etc., those picture data are transferred to a picture output unit (apparatus) as output picture data and are caused to undergo picture output. As the picture output apparatus, there are picture recording (memory) device such as printer, digital copy machine or FAX, etc., picture display device such as display, etc., and the like.
Picture data includes, as the fundamental unit, "character code", "graphic command" which is graphic description instruction such as round or square, etc., and "image data" such as natural picture described in the bitmap form, etc., and is constructed by arbitrarily combining those fundamental units.
When the picture output apparatus receives picture data consisting of character code, graphic command and/or image data, it allows this picture data to undergo development/modification (transformation) processing into data in the bitmap form suitable for output form of the picture output apparatus thereafter to sequentially write those picture data into the memory called page memory. In recent years, development/modification processing of picture data can be carried out on the OS (Operating System) by using Host computer. Also in this case, the principle is similar to the above.
The case where the picture output apparatus is printer is taken as an example. If this printer is assumed to have recording (memory) density of 600 dpi, the character code and/or the graphic command of the picture data are developed into bitmap data of the density of 600 dpi. Moreover, if the printer has color recording ability, those information are developed into bitmap data of three colors of yellow, magenta and cyan, or four colors further including black in addition to the above three colors.
In the case of image data in the bitmap form, modification (transformation) processing is implemented. In terms of the above-mentioned example, if corresponding image data has density except for 600 dpi, it is caused to undergo enlargement/compression so that it has density of 600 dpi.
Moreover, in the case where corresponding image data has gradation (tone) of 8 bits with respect to respective pixels and the gradation reproduction ability of the printer has only 3 bits with respect to respective pixels, pseudo-gradation processing such as multi-value error diffusion, etc. is implemented.
When all of character codes, graphic commands and image data belonging to one page are subjected to development/modification and write operation into the page memory is completed, the picture output apparatus serially reads out data written in the page memory from the corner of the page to send them to a picture output device. Thus, picture output is provided.
However, since development/modification processing as described above is complicated, much processing time is required. This constitutes great obstacle to high speed recording/display.
As one prior art for solving the above problem, cache is known. In accordance with the cache, an approach is employed to develop a certain character code into data in the bitmap form thereafter to write it into page memory, and to hold, at the same time, that bitmap information into a temporary memory section called cache memory. At times subsequent thereto, an approach is employed to read out, with respect to the same character code, without developing such character code, data in the bitmap form from the cache memory to write them into the page memory. Since the time required for reading out such data from the cache memory is shorter than the time required for developing character code, it is possible to write such data into the page memory at a high speed.
However, such cache function is effective only in the case where many character codes are developed in advance so that they are cached, and the time of page in a short time from start of recording/display could not be shortened.
In addition, there was the problem that the time required for enlargement/contraction of image data and/or pseudo intermediate gradation processing cannot be shortened.
Hitherto, much time is required for allowing picture data to be subjected to picture output to undergo development/modification processing so that bitmap data are provided. This constituted great obstacle to high speed picture output. In addition, the cache function was limitatively effective only in the special case.